i. Field of the Invention
The present invention relates to a method for producing an InSb thin film element for use as a magnetosensitive element, and more particularly to the use of a unique heat-treating atmosphere during production of said thin film element.
II. Brief Description of the Prior Art
It is necessary to obtain an InSb thin film element containing a crystal grain having a major axis of at least 30 .mu.m, in order to produce a magnetosensitive element of high sensitivity comprising an InSb film of 3 .mu.m(thickness). This fact was discovered previously by the inventors. For this purpose, the well known "zone-melting" technique, which is described in the paper A. R. Clawson; Intern. Conf. Thin Film, Paper 5.13, Venice, May 15-19, 1972, is suitable.
Previously, this zone-melting has been carried out in an atmosphere of a high purity inert gas such as helium or nitrogen.
The properties of an InSb thin film conventionally zone-melted in the aforementioned high purity inert gas are as follows: Hall coefficient of 100 .about. 300 cm.sup.3 /C, electron mobility of 8000 .about. 30000 cm.sup.2 /Vs, specific resistivity of 3 .times. 10.sup.-3 .about. 4 .times. 10.sup.-2 .OMEGA.cm, noise level of a bridge-type element of 0.6 .about. 15 .mu.V and S/N ratio of 40 .about. 65 dB. These values are measured under 5000 A/cm.sup.3 of current density and 10 Gauss of magnetic flux density.
However, an InSb thin film with these values is insufficient as a material for a magnetosensitive element of high sensitivity having a low noise level or a high S/N ratio. The sufficient values for a good magnetosensitive element, especially an element for a Hall head, are as follows: Hall coefficient greater than 300 cm.sup.3 /C, electron mobility greater than 30,000 cm.sup.2 /Vs, specific resistivity lower than 1 .times. 10.sup.-2 .mu..cm, noise level lower than 0.8 .mu.V and S/N ratio higher than 70 dB measured as mentioned above. Therefore, the properties of previous InSb thin films make them unsuitable for practical use, the noise level or S/N ratio of said previous thin films make them especially out of the question for use as a Hall head.